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Testing: collaborate for better design outcomes

As an outsource partner for electromechanical development teams, we supply specialist technology expertise, typically to customers for whom this function is just a small part of their development project.

Recent projects include an access ramp solenoid bolt on a hovercraft; a locking mechanism for cash-in-transit security cases; and a lock for a fridge onboard a sports boat. Our collaborations usually proceed smoothly from the outset with prototype designs sailing through the test process. But occasionally, a test initiative will reveal something vital. In each case, our engineers will create a specification from the customer’s brief which includes all known aspects of the application: operating environment, life expectancy, etc.

Solenoid functionality is something that is often oversimplified. From experience, we recognise gaps in the brief and draw out requirement details such as Failure Mode Effect Analysis (FMEA) and risk-based analysis. But we can’t imagine every eventuality – which brings us to testing.

Testing is the one development process that should never be underestimated. The danger of testing inadequately, or in a way not representative of the application, is that system limitations or weaknesses may not be revealed before production parts are ordered and installed.

When our customers engage with us, they get testing as part of the development support package. Initially, it’s a lab bench test. We can, for example, soak test for the million cycles required by the spec, confirm voltage ranges, check power consumptions or verify solenoid stroke forces meet the spec. But we cannot replicate the end-use environment – and that is critical.

Filling the gap?Real-life testing fills the gap that inevitably arises during development – the gap between our knowledge of solenoid and actuator capability, and the customer’s understanding of the challenges faced in the application’s environment. When collaborative testing is undertaken thoroughly, it brings both parties together in an exercise that everyone understands. We often uncover things we would have liked to know sooner but forgot to ask, or that the customer neglected to mention.

In the sports boat example, we designed a robust electric lock mechanism for a drawer-style onboard fridge. Bolt strength was a key feature. We couldn’t quantify the true forces in the lab, and nor could the customer prior to taking the craft to sea. During the real-life test (a sea trial) with the boat wound up to around 50 knots, our prototype lock gave way under the pounding of the hull over the water. The test resulted in a stronger bolt being designed.

With the cash-in-transit case lock, our design met stringent usability conditions, delivered the impregnable security required. The live test programme comprised extensive field trials with security operatives using the new case, fitted with pre-production lock units. Reports soon surfaced of some cases springing open when dropped. That G-force hadn’t been factored into the brief, but careful planning and execution of the field trial picked it up. We were quickly able to put it right.

Sometimes an application’s environment can change through unexpected third-party behaviour. During sea trials of the hovercraft, it was noticed that the maintenance crew routinely sprayed everything visible with a Waxoyl-type substance to inhibit corrosion. It began to clog the solenoid locking bolts, causing them to stick. Thanks to the test, we could prevent that occurring by advising the maintenance crew and recommending new procedures.

I’m certain these experiences parallel those of other specialist outsource partners. My advice to the customers of those expert companies is to recognise that collaborative testing is vital and do ensure that you make use of all the test expertise that is offered to you.